1. Field of the Invention
The present invention relates generally to a biasing circuit for a power amplifier, and more particularly, is directed to a biasing circuit for a non-switching type power amplifier.
2. Description of the Prior Art
In the prior art, various biasing circuits for Class AB power amplifiers have been proposed in which, in order to reduce the generation of switching distortion, a biasing voltage is varied or modulated in accordance with the amplitude of an output signal to render the circuit of the non-switching type.
With such prior art biasing circuits, however, when the biasing voltage is modulated in accordance with the amplitude of the output signal, a problem of non-linear distortion being generated in the biasing circuit may arise as a result of the existence of a non-linear element, such as a transistor or the like, in the signal transmission path.
Further, according to such prior art biasing circuits for the type AB-class power amplifier, if a MOS-FET (field effect transistor) is used as an amplifying element in a power amplifying stage, non-linear distortion is generated in the range where the mutual conductance of the MOS-FET is relatively small. However, no biasing circuit for the above described power amplifier, in which the generation of such non-linear distortion is removed, has been proposed.